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Methods for isolation by culture, and subsequent molecular identification, of phytoplasmas from plants sourced in the field
No full textPhytoplasma axenic cultivation was recently achieved using as a source micropropagated phytoplasma infected periwinkle shoots from the collection established more than twenty years ago. Following these results, further work was carried out to verify the possibility of achieving axenic phytoplasma cultivation from field collected phytoplasma-infected samples. Shoots showing typical symptoms of phytoplasma infection, together with asymptomatic ones of the same species, were employed. After phytoplasma identification by PCR/RFLP analyses, midribs stripped from fresh leaves were selected for phytoplasma cultivation. From each sample two midribs were surface sterilized for 1 min in 1% NaClO; ends were then discarded and two half midribs per sample were used for tube inoculation following reported procedures. Uninoculated tubes and tubes inoculated with midribs from healthy shoots were also processed under the same conditions. Colonies were obtained only from tubes inoculated with symptomatic plant material and purified by filtering three times through 0.8 μm filters. Several purified colonies were separately collected from three plates per strain, and subjected to nucleic acid extraction by DNeasy Plant Minikit (Qiagen, Germany). At the same time nucleic acid was also extracted from the corresponding tubes containing pure cultures by a phenol/chloroform based method.
Phytoplasma identification was carried out by specific PCR assays on 16S rDNA gene with general and group specific phytoplasma primers. Identification of detected phytoplasmas was done using RFLP analyses with appropriate restriction enzymes (in accord with phytoplasma isolated), and allowed the confirmation of phytoplasma nucleic acid presence. The profiles obtained by restriction of amplicons from liquid cultures and from purified colonies were identical to the ones of the original strains. The results of this study clearly confirm that phytoplasmas can grow independently from the plant host(s) and can also be isolated from field infected plants, with little modification to the procedure employed for phytoplasma isolation from strains maintained in micropropagated periwinkle collection
Cultivation of several phytoplasmas from a micropropagated plant collection
No full textThe recognition that certain plant diseases were associated with mycoplasmalike
structures in the sieve-tubes was first reported by Doi and coworkers in 1967
who extended this observation by confirming possible disease causation, and their
similarity to mycoplasmas, by showing that disease symptoms could be ameliorated
by treatment with tetracycline (Ishiie et al., 1967).
Hitherto, these diseases - referred to as the aster yellows group - had been thought to be
caused by viruses. In animals and humans, mycoplasma infections had similarly often
been regarded as viral in nature due partly to their filterability through membranes
of small pore size but also due to the inability to culture the infectious organism in
common bacteriological media.
Many workers, mainly plant pathologists rather than mycoplasmologists, took up the
challenge to culture these organisms. An early outcome of this effort was the culture
of spiroplasmas – microorganisms derived from insects capable of causing plant
diseases following infection of the sieve tubes. This distinct group of organisms grew
readily in mycoplasma media formulations whereas the mycoplasma-like objects
(phytoplasmas) did not and a possible reason was that a closer alignment of media
to sieve-tube sap composition was required. Morphologically the two groups were
quite distinct, spiroplasmas having a spiral structure as the name suggests whereas
phytoplasmas were generally pleomorphic.
Some reports of successful phytoplasma culture were published (Lombardo and
Pignattelli, 1970; Lin et al., 1970; Giannotti and Vago, 1971; Ghosh et al., 1975)
but none proved repeatable and as the years of failure increased, hope of cultivation
decreased to such an extent that some plant workers came to consider that phytoplasmas
were indeed uncultivable (reviewed in Maramorosch, 2011).
Over forty years had elapsed since Doi’s publication but there were workers who
believed culture to be possible and a collaboration was initiated in 2008 between
Bologna University and Mycoplasma Experience. Early success was definitely not
anticipated and a lengthy process of medium modification/alignment to sieve-tube sap
composition was envisaged
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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